Torsional damper device for a clutch disk

ABSTRACT

A torsional damper device comprises coaxial parts adapted to rotate relative to one another within predetermined limits. Two of the coaxial parts mesh together with clearance, the meshing portions defining predetermined limits of relative angular movement. A circumferentially acting elastic element is disposed between these two coaxial parts to resist such relative angular movement. A centering device cooperating with the meshing portions is adapted to urge the two coaxial parts circumferentially towards a rest position between the predetermined limits of relative angular movement. These two coaxial parts are formed with shoulders and the centering device comprise at least one elastic member, constituting part of the circumferentially acting elastic element, colocated with the meshing portions. A respective bearing member is disposed between each end of the elastic member and the associated shoulder. Thus the elastic member bears on the shoulders through the intermediary of the bearing members. Each bearing member is formed with a concave dihedron and when the two coaxial members are in a rest position the shoulders define a complementary dihedron. At least one of the bearing members is in one piece with the elastic member, whose corresponding circumferential end is shaped to form the corresponding dihedron.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention generally concerns torsional damper devices of thekind comprising at least two coaxial parts mounted to rotate relative toone another within a defined range of relative angular movement andcircumferentially acting elastic means disposed between said parts inthe circumferential direction resisting such relative angular movement.

2. Description of the prior art

This type of torsional damper is normally incorporated in the design ofa clutch disk, particularly for automobile vehicles, in which case onerotating part comprises a friction disk designed to rotate with a firstshaft, in practice a driving shaft and the motor output shaft in thecase of an automobile vehicle, whereas another of said rotating parts iscarried on or itself constitutes a hub designed to rotate with a secondshaft, in practice a driven shaft and the gearbox input shaft in thecase of an automobile vehicle.

This type of device permits regulated transmission of rotational torqueapplied to one of its rotating parts where the other is itself subjectto a rotational torque. It is thereby able to filter vibrations whichmay arise at any point in the kinematic system in which it isincorporated, extending from the motor to the driven road wheels in thecase of an automobile vehicle.

The present invention is more particularly directed to the case where,in order to delimit relative angular movement between two coaxial partsof a torsional damper device of this kind, there are provided betweenthe latter meshing means, with clearance, cooperating with centeringmeans adapted to urge said coaxial parts in the circumferentialdirection towards a rest position intermediate the limits of theirrelative angular movement.

This is the case, for example, in the torsional damper device which isthe subject of French Pat. No. 2,242,606 filed Aug. 29 1973 and in thepatent of addition thereto No. 2,270,491 filed Apr. 12 1974.

In both cases, the torsional damper device concerned in practicecomprises three coaxial parts successively rotatable in pairs and thosebetween which the meshing means with clearance are disposed are thosedesigned to operate at low values of torque.

The centering means provided between these coaxial parts to urge them inthe direction towards an intermediate rest position comprise at leastone elastic member constituting part of the circumferentially actingelastic means disposed between said coaxial parts, colocated with themeshing means of the latter and adapted, when these coaxial parts are inthe rest position, to bear at each of its circumferential ends against ashoulder on each of said coaxial parts.

In the aforementioned French patent No. 2,242,606 and the patent ofaddition No. 2,270,491 thereto, a helical coil spring is used.

For improved bearing engagement of this spring at its circumferentialends and thus for improved retention in position of the latter there isprovided, in the subject French patent and its patent of addition, inassociation with each of said circumferential ends of this spring abearing member adapted to be disposed between the latter and thecorresponding shoulders of the two coaxial parts concerned.

For appropriate radial retention of a bearing member of this kind andthereby of the elastic centering member, there is further provided, inthe patent of addition concerned, on this bearing member and adapted tocooperate with the corresponding shoulders of the coaxial partsconcerned, a concave dihedron, said shoulders themselves forming, in therest position of the assembly, a dihedron which is complementary to thatof said bearing member.

In practice, in French Pat. No 2,242,606 and its patent of addition No.2,270,491, each of the bearing members thus employed is constituted by aplate separate from the elastic centering member with which it isassociated.

This arrangement, which has proved and may still prove satisfactory, hasthe disadvantage of necessitating the use of two distinct parts inaddition to the elastic centering member, which increases manufacturingcosts and complicates assembly.

A general object of the present invention is an arrangement which,whilst being with advantage able to be employed without modification ofother constituent parts of the torsional damper device concerned,permits this disadvantage to be avoided, conferring also otheradvantages.

SUMMARY OF THE INVENTION

The invention consists in a torsional damper device comprising at leasttwo coaxial parts adapted to rotate relative to one another withinpredetermined limits of relative angular movement, means adapted toprocure meshing, with clearance, between said at least two coaxial partsand to define said predetermined limits of relative angular movement,circumferentially acting elastic means disposed between said at leasttwo coaxial parts in the circumferential direction adapted to resistrelative angular movement between said at least two coaxial parts, andcentering means cooperating with said meshing means adapted to urge saidat least two coaxial parts in the circumferential direction towards arest position intermediate said predetermined limits of relative angularmovement, in which device said at least two coaxial parts are formedwith shoulders and said centering means comprise at least one elasticmember constituting part of said circumferentially acting elastic meanscolocated with said meshing means and a respective bearing memberdisposed between each end of said at least one elastic member and anassociated one of said shoulders on said at least two coaxial parts,whereby said at least one elastic member is adapted to bear on saidshoulders through the intermediary of said bearing members, and whereinsaid bearing members are each formed with a concave dihedron, saidshoulders are each adapted to form, when said at least two coaxialmembers are in said rest position, a dihedron complementary to that ofsaid bearing members and at least one of said bearing members is in onepiece with said at least one elastic member, the correspondingcircumferential end of which is shaped to form the correspondingdihedron.

For example, each of the bearing members is in one piece with theelastic centering member.

Alternatively, it may be merely fastened to the latter.

Be this as it may, one and only one part is advantageously employed toconstitute the elastic centering member and the associated bearingmembers. Assembly at least is thereby simplified, while the unitarymember thus employed is accommodated in the coaxial parts concernedunder conditions identical to those usually applicable to an elasticcentering member with which are associated separate bearing members;manufacture is also simplified, especially when the bearing members arein one piece with the elastic centering member.

Moreover, in a case of this kind, and in accordance with a furtherfeature of the invention, further benefit may with advantage be derived,where required, from the extension conferred on the circumferential endsof the elastic centering member so as to form their bearing members.

In accordance with this further feature of the invention, there isassociated with the elastic centering member at least one damper pad ofelastic material disposed so as to come into operation before theclearance of the meshing means between the two coaxial parts concernedis taken up, in practice cooperating to this end with at least one ofthe circumferential ends of said elastic centering member.

For example, a damper pad of this kind may be carried by one of saidcoaxial parts, extending radially away therefrom between thecircumferential ends of the elastic centering member, so as to intersectthe path of movement on one of the latter for at least one direction ofrelative angular movement.

As a variant of, or in combination with, the previous arrangement, atleast one of the circumferential ends of the elastic centering member,and each of these, for example, carries a damper pad of this kindprojecting circumferentially towards and adapted to cooperate with itsother circumferential end.

In all cases, the use of a damper pad of this kind is advantageouslyconjugate with the use of the elastic centering member with which it isassociated.

As already mentioned, the latter forms part of the circumferentiallyacting elastic means disposed between the two coaxial parts concerned,or even constitutes these of itself, and these two coaxial parts arethose designed to operate at low values of torque.

In the case of an automobile vehicle the function of this elasticcentering member is to filter so-called dead point noise which may ariseat idling speeds with no gear engaged by virtue of inevitable assemblyclearances between the various gears of the gearbox and cyclicvariations in the motor output.

On starting, especially in cold weather, the gearbox oil in which thesegears are immersed has a relatively high viscosity and the torque at thegearbox input shaft, which forms the driven shaft, commonly referred toas the drag torque, is therefore itself relatively high, beingsufficient in all cases for the elastic centering member to be of itselfcapable of avoiding total taking up of the clearance of the meshingmeans provided between the two coaxial parts between which it isdisposed.

Under cruising conditions, on the other hand, the viscosity of thegearbox oil decreases in inverse proportion to the temperature, and thesame applies to the corresponding drag torque, as a result of which, dueto cyclic variations in the motor output, there may result on each suchvariation total taking up of the clearance of the meshing means providedbetween the two coaxial parts concerned, and thus a noisy impact betweenthe corresponding teeth of the latter.

The damper pad or pads provided in accordance with a further feature ofthe invention advantageously enable this noise to be eliminated.

Other objects and advantages will appear from the following descriptionof examples of the invention when considered in connection with theaccompanying drawings, and the novel features will be particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway view in elevation of a torsional damperdevice in accordance with the invention in the direction of the arrow Iin FIG. 2.

FIG. 2 is a view of it in axial cross-section on the broken line II--IIin FIG. 1.

FIG. 3 is a partial view of it in transverse cross-section on the lineIII--III in FIG. 2 to a larger scale with the two coaxial partsconcerned in the rest position.

FIG. 4 is a perspective view of the elastic centering member employed inaccordance with the invention between these two coaxial parts, with thebearing members which are an integral part of it.

FIG. 5 is a view analogous to that of FIG. 3 for another position of thecoaxial parts concerned.

FIGS. 6 and 7 are views respectively analogous to those of FIGS. 3 and 5relating to an alternative embodiment.

FIGS. 8 and 9 are views analogous to that of FIG. 6 and relating torespective further embodiments.

FIG. 10 is a view analogous to that of FIG. 4 and refers to a stillfurther embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

These figures illustrate by way of example the application of theinvention to a torsional damper device which, designed to constitute aclutch disk for an automobile vehicle clutch, comprises in successionand mounted so as to rotate relative to one another in pairs threecoaxial parts namely a part A, essentially consisting of a hub 10, apart B essentially consisting of an annular flange or hub flange 11surrounding the center part of the hub 10, and a part C, essentiallyconsisting of two annular flanges or guide rings 12 which, disposed oneon each side of the hub flange 11 and, like the latter, surrounding thehub 10, are attached to one another by spaced axial pegs 14 passing withclearance through openings 15 provided for this purpose in said hubflange 11.

Consisting in practice of a clutch disk, the coaxial part C carries afriction disk 16 of which the flange 17, which may be divided circularlyinto vanes, is attached by rivets 18 to one of the guide rings 12 and ofwhich the friction facings 20, disposed on opposite sides of said flange17, are designed to be clamped up between two plates constrained torotate with a first shaft, in practice a driving shaft and the motoroutput shaft in the case, as here, of an automobile vehicle.

Conjointly, the hub 10 constituting the coaxial part A features internalsplines 21 by means of which it is constrained to rotate with a secondshaft, in practice a driven shaft, the gearbox input shaft in the caseof an automobile vehicle.

The two coaxial parts A and B are mounted so as to be rotatable relativeto one another against elastic means disposed circumferentially betweenthem, for convenience referred to as circumferentially acting elasticmeans, within limits of relative angular movement determined by meshingmeans 22 with clearance provided to this end between said coaxial partsA and B.

In practice, to constitute these meshing means 22 with clearance the hub10 features in the center part of its outside surface a peripheral rim23 along which are circumferentially distributed radial teeth 24.

Conjointly, the hub flange 11 features on its internal periphery, facingthe peripheral rim 23 of the hub 10, notches 25 by virtue of which,these being of greater angular extent, it is engaged with clearance overthe teeth 24 of the hub 10.

As will be readily understood the possible range of angular movementbetween the coaxial parts A and B is limited in each direction by theabutting engagement of the teeth 24 of the hub 10 with the correspondingflanks of the notches 25 in the hub flange 11.

Associated with the meshing means 22 with clearance implementing thislimitation are centering means adapted to urge the coaxial parts A and Bin the circumferential direction towards a rest position intermediatetheir limits of relative angular movement.

In practice, these centering means comprise at least one elastic member27 which, constituting part of the circumferentially acting elasticmeans operative between the coaxial parts A and B, is colocated with thelatter's meshing means 22 with clearance.

In practice, in the embodiment shown, only one such elastic member 27 isprovided and of itself this constitutes the circumferentially actingelastic means disposed between the coaxial parts A and B.

In other words, this elastic member 27 simultaneously constitutes saidcircumferentially acting elastic means and the associated centeringmeans.

In a manner known per se, this elastic member 27 is disposed radiallybetween the hub 10 and the hub flange 11, in a housing 29 formed by twonotches 30 and 31, the former between two teeth 24 of the hub 10 and thelatter between two notches 25 of the hub flange 11.

Each of the two notches 30 and 31 is delimited circumferentially at eachend by a respective shoulder 32, 33 and is in practice formed by virtueof radial grooves locally eliminating one or more teeth 24 and notches25.

For the rest position of the coaxial parts A and B shown in FIG. 3, theshoulders 32 and 33 of the latter are generally obliquely disposedrelative to one another, one at least of them being to this endgenerally oblique relative to a radial direction through its medianarea.

In the embodiments shown this applies to the shoulder 32 on the coaxialpart A. Be this as it may, for the rest position of the coaxial parts Aand B the shoulders 32 and 33 conjointly form between them a dihedron.

In practice, it is through the intermediary of a bearing member 34, tobe described in detail hereinafter, that each of the circumferentialends of the elastic member 27 is adapted, with the coaxial parts A and Bin the rest position, to come into bearing engagement with thecorresponding shoulders 32 and 33 of the latter.

In accordance with the invention at least one of the bearing members 34thus associated with the elastic member 27, and in practice in theembodiment shown each of the latter, is in one piece with this elasticmember 27, the corresponding circumferential end of the latter beingshaped so as to form of itself a dihedron 35 with an edge a parallel tothe axis of the assembly and complementary to the dihedron which suchshoulders 32 and 33 form between them in said rest position.

In practice, in the embodiments more particularly shown in FIGS. 1through 9, the elastic member 27 consists of an appropriately foldedmetal plate and it thereby comprises, between its circumferential ends,a succession of corrugations 37 in alternate directions.

The associated bearing members 34 are then simply constituted by theends of the plate, appropriately bent into a dihedron, with the concavesides in opposite directions.

Thus in these embodiments they are in one piece with the elastic member27 with which they are associated. This also applies to the embodimentshown in FIG. 10, as will be described hereinafter.

The corrugations 37 in the elastic member 27 may be circumferentiallyregular, all their widths being the same.

Alternatively, the width of some of these corrugations 37 may differfrom that of others.

For example, and as shown, the width p' of that at least of thecorrugations which is nearest one at least of the circumferential endsof the elastic member 27, and in practice this applies to both thesecircumferential ends in the embodiment shown, is less than that p of oneat least of the corrugations 37 in its median area, which all have thesame width in practice in said embodiment.

Be this as it may, in the embodiments shown the corrugations 37 of theelastic member 27 have a radial dimension which is less than that of theassociated bearing members 34, this dimension corresponding overall tothat of only the shoulders 32 of the coaxial part A, whereas thedimension of the bearing members 34 further corresponds to that of theshoulders 33 of the coaxial part B.

Moreover the elastic member 27 overall extends substantiallytangentially relative to a circumference of the assembly and by virtueof the dihedral configuration of the bearing members 34 which constituteits circumferential ends, it is still adequately retained in the radialdirection.

In the rest position of the coaxial parts A and B there may, as shown,be the same clearance J on each side of each of the teeth 24 of the hub10 constituting the coaxial part A, between the flanks of these teethand the corresponding flanks of notches 25 of the hub flange 11constituting the coaxial part B engaged over them.

Alternatively, there may be different clearances on each side of each ofthe teeth 24 of the hub 10 in this rest position.

Conjointly, the coaxial parts B and C are also mounted rotatablyrelative to one another, against elastic means interposedcircumferentially between them and constituted in the embodiment shownby helical coil springs 39A, 39B and 39C extending substantiallytangentially to a common circumference of the assembly and housed inpart in openings 40A, 40B and 40C formed to this end in the hub flange11, continuously in the case of the openings 40C with the holes 15 whichthe latter comprise for the axial spacers 14, and in part in openings41A, 41B and 41C also formed to this end in the guide rings 12.

The openings 40A and 41A for the springs 39A have the samecircumferential extent.

The circumferential extent of the openings 40B and 40C for the springs39B and 39C is greater than that of the openings 41B and 41C, however,the corresponding clearance being greater for the springs 39C than forthe springs 39B.

Relative angular movement between the coaxial parts B and C is limitedeither by the turns of any of the springs 39A, 39B and 39C coming intocontact with one another or through contact of at least one of the axialspacers 14 with the corresponding circumferential edge of the hole 15 inthe hub flange 11 through which it passes.

These arrangements are well known per se and as they do not constitutepart of the present invention they will not be described in more detailhere.

Similarly, by virtue of arrangements which are well known per se,friction means which will not be described in detail here are providedbetween the coaxial parts A, B and C, being activated by axially actingelastic means.

In practice, the stiffness of the elastic member 27 that the block ofelastic material constitutes in accordance with the invention is verymuch less than that of the springs 39A, 39B and 39C.

Consequently, in service, when a torque is applied to the coaxial partC, in the direction indicated by the arrow F in FIGS. 1, 3 and 5, forexample, initially only this elastic member 27 yields, until the teeth24 of the hub 10 abut against the corresponding flank of the notches 25of the hub flange 11 (FIG. 5).

As the torque to be transmitted increases, the springs 39A begin to actin their turn and then, in succession and according to the clearancebetween their respective openings 40B-41B and 40C-41C, firstly thesprings 39B and finally the springs 39C.

Conjointly, the elastic member 27 remains compressed.

When the torque changes in the opposite direction, it exerts a returnforce between the coaxial parts A and B until these coaxial parts A andB return to their initial rest position in which their respectiveshoulders 32 and 33 are facing one another.

Moreover, when the elastic member 27 is compressed and given thedisparity as specified hereinabove between their width p' and that p ofthe others, the corrugations 37 of the elastic member 27 nearest thecircumferential ends of the latter cease to be operative when compressedto the full extent of their width p' (FIG. 5).

There results an increase in the stiffness of this elastic member 27which is of particular advantage in certain applications at least,including the present application.

In other words, because of this difference in width, the elastic member27 constitutes in a very simple manner a spring of variable elasticity.

In the embodiments shown by FIGS. 6 through 9, there is associated withthe elastic centering member 27 at least one damper pad 42 of elasticmaterial disposed to come into operation before the clearance J of themeshing means 22 with clearance provided between the coaxial parts A andB is fully taken up.

In the embodiment more particularly shown in FIGS. 6 and 7, a singledamper pad 42 is provided and is carried by the coaxial part B.

In practice, it is anchored by means of a foot 43 in a notch 44 providedfor this purpose in the median area of the notch 31 in the hub flange 11forming part of the housing 29 for the elastic member 27 and, startingfrom the corresponding edge of said hub flange 11, it extends in theradial direction towards the axis of the assembly, between the bearingmembers 34 which the circumferential ends of said elastic member 27constitute.

In the rest position of the assembly (FIG. 6) the damper pad 42 thusemployed is spaced from both of the circumferential ends of the elasticmember 27.

However, on relative angular movement between the coaxial parts A and Bit intersects the path of movement of that of the circumferential endsof the elastic member 27 which corresponds to the direction in whichthis angular movement is occurring, the latter coming into abutmentengagement with it, as shown in FIG. 7, before the corresponding angularclearance J between said coaxial parts A and B is totally taken up.

In other words, when the bearing member 34 constituted by the relevantcircumferential end of the elastic member 27 bears against this damperpad 42, there remains a clearance J1 between the teeth 24 of the hub 10and the corresponding flanks of the notches 25 engaged over the latter(FIG. 7).

The circumferential extent of the damper pad 42 is naturally determinedin consequence of this.

In the embodiments illustrated by FIGS. 8 and 9, at least one of thecircumferential ends of the elastic member 27 constituted by the bearingmembers 34 associated with the latter carries a damper pad 42'projecting circumferentially towards that other end, adapted tocooperate with said other circumferential end on compression of saidelastic member 27.

For example (FIG. 8) one only of the circumferential ends of the elasticmember 27 carries a damper pad 42' in this manner.

Alternatively (FIG. 9) each of these circumferential ends carries adamper block 42' of this kind.

In the embodiment illustrated by FIG. 10, instead of being constitutedby an appropriately bent metal plate, the elastic member 127 is acircular cross-section wire also appropriately bent to include bearingmembers 134 and dihedrons 135.

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the appended claims.

For example, instead of being in one piece with the elastic member withwhich they are associated, the bearing members provided at the ends ofthis elastic member may be merely attached to the latter; this may bethe case, for example, when an elastic member of this kind consists of ablock of elastic material, the associated bearing members then being,for example, appropriately bonded to the block of elastic material, bymolding or using an adhesive, for example.

In all cases, the combination constitutes a single component.

There is claimed:
 1. Torsional damper device comprising at least twocoaxial parts adapted to rotate relative to one another withinpredetermined limits of relative angular movement, meshing means beingprovided with clearance between said coaxial parts and defining saidpredetermined limits of relative angular movement, circumferentiallyacting elastic means disposed between said coaxial parts in thecircumferential direction for resisting relative angular movementbetween said coaxial parts, and centering means cooperating with saidmeshing means for urging said coaxial parts in the circumferentialdirection towards a rest position intermediate said predetermined limitsof relative angular movement, said coaxial parts having shoulders, saidcentering means comprising at least one elastic member havingcircumferential ends and constituting part of said circumferentiallyacting elastic means colocated with said meshing means, and a respectivebearing member disposed between each end of said elastic member and anassociated one of said shoulders on said coaxial parts, said elasticmember being adapted to bear on said shoulders through the intermediaryof said bearing members, and said bearing members being formed with aconcave dihedron, said shoulders on the respective coaxial parts in saidrest position forming a dihedron complementary to that of said bearingmembers, and at least one of said bearing members being in one piecewith a corresponding circumferential end of said elastic member, saidelastic member comprising corrugations between its circumferential endsand said corrugations having varied circumferential widths so as to varythe stiffness of said elastic member in the course of relative angularmovement of said coaxial parts.
 2. Torsional damper device according toclaim 1, wherein each of said bearing members is in one piece with anassociated circumferential end of said elastic member.
 3. Torsionaldamper device according to claim 1, wherein the circumferential width ofat least one of said corrugations near at least one end of said elasticmember is less than that of at least one of said corrugations near thecenter of said elastic member so that the stiffness of said elasticmember increases with increasing relative angular movement of saidcoaxial parts.
 4. Torsional damper device according to claim 1, whereinsaid elastic member is constituted by an appropriately bent leaf spring.5. Torsional damper device according to claim 1, wherein said elasticmember is constituted by an appropriately bent piece of spring wire. 6.Torsional damper device according to claim 1, further comprising atleast one damper pad of elastic material engageable with said elasticmember and adapted to come into operation before said clearance of saidmeshing means is fully taken up.
 7. Torsional damper device according toclaim 6, wherein said damper pad is carried by at least one of saidcoaxial parts and extends radially away therefrom between said bearingmembers of the associated elastic member so as to intersect the path ofmovement of one of said bearing members in at least one direction ofrelative angular movement between said coaxial parts.
 8. Torsionaldamper device according to claim 6, wherein said one bearing member ofsaid elastic member carries said damper pad projecting circumferentiallytherefrom towards and adapted to cooperate with the other of saidbearing members.
 9. Torsional damper device according to claim 8,wherein each of said bearing members of said elastic member carries adamper pad.
 10. Torsional damper device comprising at least two coaxialparts adapted to rotate relative to one another within predeterminedlimits of relative angular movement, meshing means provided withclearance between said coaxial parts and defining said predeterminedlimits of relative angular movement, circumferentially acting elasticmeans disposed between said coaxial parts in the circumferentialdirection for resisting relative angular movement between said coaxialparts, and centering means cooperating with said meshing means forurging said coaxial parts in the circumferential direction towards arest position intermediate said predetermined limits of relative angularmovement, said coaxial parts having shoulders, said centering meanscomprising at least one elastic member constituting part of saidcircumferentially acting elastic means colocated with said meshingmeans, said elastic member having circumferential ends and a respectivebearing member disposed between each end of said elastic member and anassociated one of said shoulders on said coaxial parts, said elasticmember being adapted to bear on said shoulders through the intermediaryof said bearing members, and said bearing members being formed with aconcave dihedron, said shoulders on the respective coaxial parts in saidrest position forming a dihedron complementary to that of said bearingmembers, and at least one of said bearing members being in one piecewith a corresponding circumferential end of said elastic member, atleast one damper pad carried by one of said coaxial parts and extendingradially away from said coaxial parts between the bearing members ofsaid elastic member so as to intersect the path of movement of said onebearing member in at least one direction of relative angular movementbetween said coaxial parts, said one bearing member projecting away froman adjacent portion of said elastic member to provide clearance for thepositioning of said damper pad.
 11. Torsional damper device comprisingat least two coaxial parts adapted to rotate relative to one anotherwithin predetermined limits of relative angular movement, meshing meansbeing provided with clearance between said coaxial parts and definingsaid predetermined limits of relative angular movement,circumferentially acting elastic means disposed between said coaxialparts in the circumferential direction for resisting relative angularmovement between said coaxial parts, and centering means cooperatingwith said meshing means for urging said coaxial parts in thecircumferential direction towards a rest position intermediate saidpredetermined limits of relative angular movement, said coaxial partshaving shoulders, said centering means comprising at least one elasticmember constituting part of said circumferentially acting elastic meanscolocated with said meshing means, said elastic member havingcircumferential ends, and a respective bearing member disposed betweeneach end of said elastic member and an associated one of said shoulderson said coaxial parts, said elastic member being adapted to bear on saidshoulders through the intermediary of said bearing members, and saidbearing members being formed with a concave dihedron, said shoulders onthe respective coaxial parts in said rest position forming a dihedroncomplementary to that of said bearing members, and at least one of saidbearing members being in one piece with a corresponding circumferentialend of said elastic member, at least one damper pad of elastic materialassociated with said elastic member and adapted to come into operationbefore said clearance of said meshing means is fully taken up, saiddamper pad being fixed to and projecting circumferentially from said onebearing member of said elastic member and cooperable with the other ofsaid bearing members of said elastic member to compress said damper pad.12. Torsional damper device according to claim 11, wherein there is adamper pad fixed to and projecting circumferentially from each of saidbearing member of said elastic member, said damping pads associated withsaid elastic member eing adapted to abut each other in the course ofrelative angular movement of said coaxial parts.
 13. Torsional damperdevice comprising at least two coaxial parts adapted to rotate relativeto one another within predetermined limits of relative angular movement,meshing means being provided with clearance between said coaxial partsand defining said predetermined limits of relative angular movement,circumferentially acting elastic means disposed between said coaxialparts in the circumferential direction for resisting relative angularmovement between said coaxial parts, and centering means cooperatingwith said meshing means for urging said coaxial parts in thecircumferential direction towards a rest position intermediate saidpredetermined limits of relative angular movement, said coaxial partshaving shoulders, said centering means comprising at least one elasticmember constituting part of said circumferentially acting elastic meanscolocated with said meshing means, said elastic member havingcircumferential ends and a respective bearing member disposed betweeneach end of said elastic member and an associated one of said shoulderson said coaxial parts, said elastic member being adapted to bear on saidshoulders through the intermediary of said bearing members, said elasticmember having said bearing members integrally formed at itscircumferential ends, said bearing members having obtuse concavedihedral configuration with sides of each of the dihedral bearingmembers being engageable with complementary shoulders on the respectivecoaxial parts, said elastic member comprising a plurality ofsustantially identical circumferentially extending corrugations andbeing joined at its ends to the respective bearing members, saidcorrugations including peaks and troughs, the peak-to-peak andtrough-to-trough spacing of said plurality of corrugations being greaterthan the circumferential spacing of the endmost peak to the edge of thedihedral angle of the adjacent bearing member.